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		<h1>Pluggable Roster Support Guide</h1>
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<h2>Introduction</h2>

<p>
    This document provides instructions on how to configure Openfire's roster support to work 
    with alternate sources of roster data rather than the provided database tables.
</p>
<p>
    Consider the scenario where Openfire is integrated as the chat server solution for an existing 
    'social' application. In this application a user is linked to other users via a relationship 
    of sorts, and the system of record for the relationship data is NOT the Openfire system. 
    Using an XMPP server such as Openfire the applications benefit from the real-time nature of 
    XMPP rosters and other subscription based features such as PEP, but with the caveat that 
    the existing relationship information has to be duplicated in Openfire and could potentially
    become out of sync.
</p>
<p>
    With the introduction of pluggable roster providers, Openfire can be instructed to retrieve and 
    modify roster data that lives in alternative locations to the standard database tables. The options 
    are limitless as to what this could be, e.g. an alternative database table(s), a web service, a NoSQL 
    database etc. 
</p>

<h2>Background</h2>

<p>
    This integration requires some Java knowledge in order to implement a custom roster provider 
    for Openfire. The skill needed will vary depending on what you are trying to achieve.
    The extension approach is similar to the custom AuthProvider approach on which it is based.
</p>

<h2>The RosterItemProvider extension point</h2>

<p>
    As of Openfire 3.7.2, the class RosterItemProvider has changed from being a concrete class to an interface.
    The default implementation of this provider is the DefaultRosterItemProvider, which as the name suggests is the 
    version of this provider Openfire will use if not overriden. The DefaultRosterItemProvider uses the Openfire 
    database to retrieve roster information. 
</p>
<p>
   The steps to get Openfire using a custom RosterItemProvider are described below.  
    <ol>
        <li>Write a class that implements RosterItemProvider, providing your own business logic.</li>
        <li>Make the class available in a jar and make this available to Openfire by placing it in the lib directory.
	There are numerous ways to package a jar with this class inside it, popular build systems such as Gradle and Maven
        can make your life easier.</li>
        <li>Set the property 'provider.roster.className' to be the full name of your class, e.g. 'com.foo.bar.MyRosterItemProvider'. 
        </li>
        <li>Restart Openfire. Your custom class should now be handling all the roster based operations.</li>
    </ol>

</p>

<h2>Frequently Asked Questions</h2>

<p>
    <ol>
        <li><b>Do I have to compile my custom class into the Openfire jar?</b> No, the class only needs to be visible on the Openfire classpath.</li>
        <li><b>How do I ensure my custom class is visible on the Openfire classpath?</b> Just place your new custom library in the Openfire lib directory,
        this will ensure it is automatically available at startup.</li>
        <li><b>Will I have a degradation in performance using a custom RosterItemProvider?</b> It completely depends on your implementation. As with any 
        Openfire customisation or plugin, badly written code has the potential to cause Openfire to perform slower. Use performance testing tools such 
        as Tsung to ensure issues haven't been introduced.</li>
        <li><b>How can I have my custom class connect to another DB/Web service/NoSQL store etc?</b>
	This is outside of the scope of this documentation and is your choice as a developer. If you are looking to externalize properties like 
	connection details, the Openfire properties mechanism and the JiveGlobals class are good places to start investigating.</li>
        <li><b>Can I have multiple RosterItemProviders, in a similar vein to the HybridAuthProvider?</b> No, this feature is currently not implemented.
	Get involved if you feel a need to have it!</li>
    </ol>

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